18,159 research outputs found
Quantum Electrodynamics vacuum polarization solver
The self-consistent modeling of vacuum polarization due to virtual
electron-positron fluctuations is of relevance for many near term experiments
associated with high intensity radiation sources and represents a milestone in
describing scenarios of extreme energy density. We present a generalized
finite-difference time-domain solver that can incorporate the modifications to
Maxwell's equations due to vacuum polarization. Our multidimensional solver
reproduced in one dimensional configurations the results for which an analytic
treatment is possible, yielding vacuum harmonic generation and birefringence.
The solver has also been tested for two-dimensional scenarios where finite
laser beam spot sizes must be taken into account. We employ this solver to
explore different types of counter-propagating configurations that can be
relevant for future planned experiments aiming to detect quantum vacuum
dynamics at ultra-high electromagnetic field intensities
Functional response of Telenomus remus Nixon (Hymenoptera, Scelionidae) to Spodoptera frugiperda (J. E. Smith) (Lepidoptera, Noctuidae) eggs: effect of female age.
Resposta funcional de Telenomus remus Nixon (Hymenoptera, Scelionidae) sobre ovos de Spodoptera frugiperda (J. E. Smith) (Lepidoptera, Noctuidae): efeito da idade da fêmea. A resposta funcional de fêmeas de Telenomus remus com 24 h e 48 h de idade foi observada em ovos de Spodoptera frugiperda. O experimento foi conduzido em câmara climatizada regulada a 25 ± 1°C, 70 ± 10% UR e fotofase de 12h. As fêmeas de T. remus foram alimentadas com mel e mantidas individualmente por 24h em tubos de vidro que continham 25, 50, 75, 100, 150, 200, 250 ou 300 ovos de S. frugiperda. Foi adotado o delineamento experimental inteiramente casualizado com 10 repetições. Os parâmetros avaliados para a construção da curva de resposta funcional foram o parasitismo médio diário, a taxa de busca e o tempo de oviposição. Foi observado que com o aumento da densidade de ovos também cresce o parasitismo em fêmeas com 24 h e 48 h de idade e que há uma tendência de estabilização do parasitismo na densidade de 150 ovos/fêmea. Os resultados mostraram uma curva de resposta funcional do tipo II para fêmeas de T. remus com 24 h e 48 h de idade
High-performance 16-way Ku-band radial power combiner based on the TE01-circular waveguide mode
This work presents a 16-way Ku-band radial power combiner for high power and high frequency
applications, using the very low loss TE01 circular waveguide mode. The accomplished design shows
an excellent performance: the experimental prototype has a return loss better than 30 dB, with a balance
for the amplitudes of ( 0.15 dB) and ( 2.5 ) for the phases, in a 16.7% fractional bandwidth (2 GHz
centered at 12 GHz). For obtaining these outstanding specifications, required, for instance, in highfrequency
amplification or on plasma systems, a rigorous step-by-step procedure is presented. First, a
high-purity mode transducer has been designed, from the TE10 mode in the rectangular waveguide to
the TE01 mode in the circularwaveguide, with very high attenuation (>50 dB) for the other propagating
and evanescent modes in the circularwaveguide. This transducer has been manufactured and measured
in a back-to-back configuration, validating the design process. Second, an E-plane 16-way radial
power divider has been designed, where the power is coupled from the 16 non-reduced-height radial
standardwaveguides into the TE01 circularwaveguide mode, improving the insertion loss response and
removing the usual tapered transformers of previous designs limiting the power handling. Finally, both
the transducer and the divider have been assembled to make the final radial combiner. The prototype
has been carefully manufactured, showing very good agreement between the measurements and the
full-wave simulationsThe authors would like to thank INMEPRE S.A., the diligence
in the manufacturing process. This work was supported
by the Spanish government under Grant (ADDMATE) No.
TEC2016-76070-C3-1/2-R (AEI/FEDER/UE) and the program
of Comunidad de Madrid S2013/ICE-3000 (SPADERADARCM
Capacidade de dispersão de Telenomus remus Nixon (Hymenoptera: Scelionidae) na cultura do milho.
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